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An Astronomical First: Ground Telescope Spots Transiting Habitable Planet

By James Maynard, Tech Times

The exoplanet 55 Cancri e has been observed passing in front of its star for the first time by a ground-based telescope. What do we know about this strange planet?
(Photo : NASA/JPL-Caltech/R. Hurt (SSC))

The exoplanet 55 Cancri e has been seen transiting, or passing between its sun and our planet, for the first time ever, using a moderate ground-based telescope.

Astronomers utilized the 97.5 inch Nordic Optical Telescope, located on the island of La Palma, Spain. This instrument is not large by today's standards, nor does it offer advantages of space-borne observatories.

This super-Earth orbits 55 Cancri, a star much like the Sun. Before this latest investigation, transits of the alien world could only be observed using telescopes in space. These events can only be seen in systems where a planet orbits directly between its parent star and the Earth. A faint dimming of light can be recorded by astronomers, like a flying insect passing in front of a distant light bulb. In the case of 55 Cancri, this dimming reduces the brightness of the star by 0.05 percent, or one part in 2000.

"Our observations show that we can detect the transits of small planets around Sun-like stars using ground-based telescopes. This is especially important because upcoming space missions such as Tess and Plato should find many small planets around bright stars," Ernst de Mooij from Queen's University Belfast in the United Kingdom, said.

The Transiting Exoplanet Survey Satellite (Tess), managed by NASA, is scheduled for launch in 2017, on a two-year mission to discovery worlds orbiting alien suns. In 2025, the European Space Agency (ESA) is planning to send the PLAnetary Transits and Oscillations of stars (Plato) observatory into space, in order to add to the list of known planets outside the Solar System.

The planetary system surrounding 55 Cancri is a neighbor of our solar system, located just 40 light years from the Sun. This star is barely visible to the naked eye under very dark skies, seen in the constellation of Cancer. The main yellow dwarf star possesses another solar companion, a small red dwarf, which orbits 1,000 astronomical units (AU's) from its larger companion, 25 times the distance between the Sun and Pluto.

The planet 55 Cancri e has a mass about 7.8 times as great as the Earth, and a diameter about twice that of our home planet. The world may be a carbon planet, rich in organic chemicals, colored reddish-brown from mass quantities of hydrocarbons on its surface. The world races around its sun so quickly, that a year on 55 Cancri e lasts just 18 hours. The planet is tidally locked to its parent star, with one face permanently facing the stellar body, in much the same way the Moon always has one face turned toward the Earth. Temperatures on the hot side of 55 Cancri e can exceed 3,000 degree Fahrenheit, hot enough to melt iron.

Future research will study the planet, searching for water vapor in the atmosphere, which could have been driven off the surface by searing temperatures